Dental articulator



March 2, 1954 H. J. THOMPSON DENTAL ARTICULATOR Filed Aug. 25, 1952 Mai/V702 s N H M 0 7 m 4 10! k Patented Mar. 2, 1954 UNITED STATES EPA-TENT F F ICE 2,670,53&

DENTAL ARTIOULATOR Harold J. Thompson, Minneapolis, Minn A pearances-1:81:25, 1952; Serial NoL'306',l14

' This invention relates to dental articulators and to the making of dentures 'by' means of an ticulation in the construction of dentures by first considering the mall-function ofteeth in their natural state, then assuming that corrective measures, either natural or artificial, which will solve problems arising from the occlusal topography of humanteeth Will also solve the same problems arising from the same deiects in the occlusal topography of the teeth in the ease of dentures Mechanical forces of mastication normally directed will be distributed by the supporting'tissue structures. If these mechanical forces are abnormally directed, there will be a reaction of the supporting tissues resulting in local stresses 0r loads in excess of that which the tissue structure'is capable of withstanding. These local and concentrated forces first cause an irritation and subsequently a traumatic condition which ultimately may become'irreparable; A large number of oases oi'pyorrhea are directly-attributable to this cause alone. condition results from 'a' localization of high stresses caused by the strength musclesof the jaw being" concentrated in a much smallerar'ea' than nature. intended. Since the natural building bulls: in the tissues or'the gums is no greater than necessary for distributed forces, an unusually greater concentration of force willcause a breakdotvn of the supporting tissues at the particular region of force As ap'remise therefore in'de'veloping an articulator which will aid-in the construetion of'dentures which give balanced occlusion for comfort and eificient mastication I have discovered that the same forces that operate to promote long healthy function of the natural dentition in their ordinary situation also are rccuired to stabilize and promote retention potential in artificial dentures. In order-to; reproduce dentures which will evenly distribute stresses between the upper and'lower teeth thereof it is necessary that they not-only-fit in centric relation during immobile occlusion but will also evenly distribute the stresses'duringall or thenormal movements produced by the. mandible. during the biting and chewing of food.

In the case'of natural dentition, cusps. out'or alignment can cause disharmonious function in specific areas of the mouth which, if not corrested, will result in trauma of the gum tissue The reason for the traumatic towards retention of the plate.

6. Claims. (mica-3a;

which are abnormally stressed thereby-.7 mproper corrective measures, although correc n thespeoific. fault atone point, can result: in progressive failure of a number of teeth andsurrounding tissue. Similarly in prosthetic dentiti'on cusps. out of" alignment can cause a forc which-is transmitted by the dental plate tothe gum tissue and cause local irritation at th point of stress." Unfortunately, the point of; irritation inary high spot the" misalignment. not. in any way corrected but the stress is shifted to anew area: with the. original irritated area now being out of intimate contactand failing to. contribute Furthermore, miscorrectionzmerely intensifies the lack of retention without correcting'the basic trouble.

It'is'therefcre a. general object of the invention to provide a dental articul'ator which will simply and positively indicatethe precise facet construction of both'the' anterior and the posterior teeth necessary to produce a matching set of upper and 'jawsiduring mastication are guided 'by surface formation of the 't'e'mperoemandibular joint itself. However, in the case of articulators which have been constructed according to the condylar inclination theory the calculated mechanical coaction ofthe condyle'in contact with the glenoid fossa'does not result-in an instrument which can predict the proper faceting ofthe individual tooth cusps during the actual'c'onstruction of the dental plates.

I have developed a new theory of articular occlusion which I call the functional facet theory and which states in substance that the movements) of the jaw are guided by automatically controlled bi-lateral sets of muscles acting on a compound-complex lever of the third class. The muscle action upon each bi-lateral joint may be in unison with the other, in opposition therewith, or in multiple combinations of actions upon the mandible as a whole, the condyle of which functions as a facultative fulcrum with the pull of the muscles being the determining guidance. With this in evidence it is possible to arrive at a definition of true centric relationship, namely the center of muscle pull when the mandible is in its most retruded position in relation to the glenoid fossa. This is important since an exact starting point can be obtained and transferred from the mouth to the articulator by means of trial plates and wax check blocks. This furnishes an exact and correct starting point for each movement away from centric, always under controlled guidance. I have performed numerous experiments to arrive empirically at the pattern of movement between the teeth of the mandible or lower jaw relative to the teeth of the upper jaw. These experiments were performed by taking plaster casts from normal dentulous human mouths and mounting them in free suspension from three points, then imitating the natural movements of the jaw during mastication while at the same time recording and preserving in clay pantographic tracings in the attempt to arrive at a standard and uniform Lil action which could be used in the construction of an articulator. From these experiments I discovered that the tracings obtained were surprisingly uniform regardless of the size or shape or combination of shapes of the dental arches.

The articulator which I have developed in the light of these experiments simulates lateral shifting of the mandible relative to the upper iawas well as forward and backward movement,

either simultaneously or consecutively to obtain r -a variety of combinative movements.

Dentures made with the use of my articulator allow intricate movements of the users jaw which result in an unusually high degree of satisfaction. Dental plates, which have previously given trouble, when corrected in my articulator are invariably completely satisfactory since the correction is made at the occlusal surfaces of the plates and not at the point of irritation upon the patients gun. Plates constructed under my method utilize teeth having cusps of average height, no advantage being noted in the use of deep grooves and high cusps on the one hand or -in flat teeth on the other hand. In other words the dentures constructed by my method con-' -ments between human jaws with teeth having facets worn naturally therein.

It is a still further object of the invention to provide for an articulator responding simply and eiiiciently to contoured guiding or hearing surfaces between the relatively movable upper and lower portions thereof, the formation of the contoured surfaces being simply selected according to the general pattern of movement between the occlusal surfaces of the normal dentulous mandible with relation to the dentulous maxilla with the articulator pre-set in spaced relation even before beginning the setting and grinding of the individual artificial teeth.

These and other objects and advantages of this invention will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

Fig. 1 is a side elevation of my articulator showing partly completed dentures mounted therein in dotted line representation;

Fig. 2 is a front elevation of my articulator;

. Fig. .3 is a top elevation of the articulator;

Fig. 4 is a diagrammatic representation of the suspension means showing the relative positions between the bearing pins and the concave surfaces of the sockets when the upper structure is moved directly backwards with respect to the base structure; and

Fig. 5 is a diagrammatic representation simi- .lar to that of Fig. 4 showing the relative positions of the bearing pins and the concave surfaces of the socket members when the upper structure is moved difierentially over the socket surfaces. I

Referring now to the drawings, my articulator comprises a. rigid base structure R for supporting the entire mechanism. The structure R comprises a base or lower platform 10 to which may be secured a cast mount H which will position and retain plaster casting material upon the base Iii.

At the rear of the base H), is an upstanding portion i2 which in turn comprises a pair of vertical parallel standards l3 and a cross bar i l slidably mounted upon the standards 13 and adjustable therewith by thumb nuts IS. The cross bar in turn has an extending gooseneck It which terminates at its upper portion in a sleeve ll. Slidably mounted within the .sleeve I! is a resilient hold-down member 18.

bears upon a cam surface 23 at the rear of the movable upper structure designated generally by the letter M.

The movable upper structure M in turn comprises an upper platform 24. A laterally extend- .ing arm 25 is secured integrally therewith to form a generally T-shaped platform. The lateral -arm 25 has at each side an abutment or knob 26 and 27 which may be utilized manually for manipulating the articulator. Removably secured to the platform 24 is an upper cast mount 28 .which may have a threaded upstanding portion extending through the platform 24 and secured :as at 29 by a cooperating threaded element.

with the rigid base structure R through a three- .point suspension means S. For the sake of con- -venience, I prefer to use a pin and socket arrangement as shown. The suspension means S The movable upper structure M is connected is symmetrically positioned with respect to both the base structure and upper structure in its centric relationship. In particular, the suspen- :sion means S comprises a left socket bearing 30 which is secured to the cross bar 14 as by screws :3l. A right socket bearing 32 is similarly posiportion. Since the front bearing pin 40 has movedbut a short distance from centric and on a surface having a lower rate of curvature, the front portion of the movable upper structure will have raised to an even lesser degree. Although the foregoing description of the manipulation of the articular has been made with reference to the twelve opposed anterior teeth, the samewprocedure is employed throughout the entire operation. The individual teethare ground so as to acquire facet surfaces which will be in contacting relationship throughout the complex differential movements given to the articulator as above described. The posterior teeth are next .placed upon the bite plates in a similar manner and facet surfaces are ground thereon to conform to the same movements which were given the upper structure in articulating the anterior teeth.

In my experimental work,.to determine the proper points of suspension and rates of curvature in the socket bearings, I was surprised to discover that the movements of the mandible in a human dentulous mouth with respect to the maxilla was very nearly exactly repetitious for all types, shapes and sizes of jaws. The measurements which I found to give me the best results were a thirteen-sixteenths of an inch radius for the curvatureof the surfaces of the rear socket bearings and one and one-half inches radius for the contoured surface of the forward socket bearing 33. Although a spherical surface segment was found to be the best form for practical reasons in the manufacture of the articulator, it is understood, of course, that only the rear halves of all the socket bearings are actually employed during articulation. Since the rate of curvature of the socket bearings is variable with the distance between them, I found that the central depression points 43 of the rear socket bearings should be one and seven-sixteenths inches on each side of the center line. Also, the relative position of the front socket hearing was found to befour and five-sights inches from the front pin to the line connecting the rear bearing pins. Since it is the differential and complex movement of the upper structure with respect to the base structure that determines the success of my articulator, any variations of the dimensions which I have given that will produce the same movements would be acceptable inbuilding an equivalent articulator. It is to be noted, however, that I have selected my dimensions on the basis of conservation of structural material on the one hand as opposed to freedom of operation and balanced design on the other hand.

- It may thus be seen that I have devised a new and useful articulator, the function of which is based on the almost unanimous similarity of movements between the upper and lower jaws of the normal human dentulous mouth at the occlusal or faceted tooth surfaces. My articulator has thus been simply developed from the end result rather than attempting to devise an articulator, on the other hand, which would reproduce all the complex movements of the jaws under the condylar theory which, with respect to articulation, disregards the effect of ultimate faceting acquired by normal teeth during the use and wear thereof. It is to be further noted that all my faceting of artificial teeth is accomplished while maintaining the upper structure in positive, three-point suspension with relation to the base structure, the two structures being relatively movable laterally as well as longitudinally on 8 1 contoured surfaces. As a result there will be no latitude or guess work in selecting the proper occlusal pattern throughout the articulation of artificial teeth when using my articulator.

It will, of course, be understood that the movable upper structure may be fixed while the fixed base structure is caused to be relatively movable and that various other changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of my invention which, generally stated, consists in the matter shown and described herein and. set forth in the appended claims.

What I claim is:

1. In a dental articulator a supporting structure having a base with a lower cast mount thereon for securing rigidly thereto the cast of a lower jaw, a movable upper structure normally parallel to said base and having an upper cast mount thereon for securing rigidly thereto the cast of an upper jaw, and a three-point suspension between the movable upper structure and the supporting structure comprising two spaced rear suspension members, each having a sliding connection including a bearing member on the upper structure with a concave bearing surface in the supporting structure, and a front suspension member having a sliding connection including a bearing member mounted on the upper structure and a concave bearing surface in the supporting structure said two rear concave surfaces having a greater rate of curvature than that of the front concave bearing surface. a W

2. In a dental articulator a base member having a rearward pair of contoured bearings positioned upwardly and rearwardly of the surface thereof and a forward contoured bearing surface centrally and forwardly thereof, said base surface being adapted to mount a lower dental casting thereon, and a movable upper structure having depending bearing members engageable'with the forward and rearward contoured bearing surfaces and an upper dental casting mount intermediate the ends thereof, said contoured bearings having indentations. at the lowermost portion of each of the contoured bearings for indicating the centric position of the upper jaw casting with relation tothe lower jaw casting whereby movement of the upper movable structure upon said bearing surfaces will similate the relative movement of the jaws in a dentulous human mouth with the facets of the occlusal surface of the upper and lower teeth operating in natural contact.

3. In a dental articulator a supporting structure having a base with a lower cast mount thereon for securing rigidly thereto the cast of a lower jaw, a movable upper structure having an upper cast mount thereon for securing rigidly thereto the cast of an upper jaw, and a three-point suspension between the movable upper structure and the supporting structure comprising two spaced rear suspension members, each having an arcuately movable connection between the upper structure and the supporting structure, and a front suspension member having an arcuately movable connection between the upper structure and the supporting structure said arcuate connection at each of said spaced rear suspension members having a rate of curvature in excess of that of the arcuate connection at the front suspension member.

4. In a dental articulator a supporting structure having a base with a lower cast mount thereon for securing rigidly thereto the cast of a lower 9 jaw, a movable upper structure overlying said base and having an upper cast mount thereon for securing rigidly thereto the cast of an upper jaw, and a three-point suspension between the movable upper structure and the supporting strum ture comprising a pair of spaced concave rear bearing members in spaced relation secured to one of said upper structure and supporting structure, a pair of rear pin bearing members adapted to engage respectively the concave bearing members, said pin bearing members being attached to the other of said upper structure and supporting structure, and a front suspension member having a sliding connection including a concave bearing member mounted on the fore of one of said upper structure and supporting structure and a front pin bearing member secured to the other of said upper structure and supporting structure, said forward concave bearing surface having a lesser rate of curvature than that of said pair of rear concave bearing surfaces.

5. In a dental articulator a base member having an upwardly facing surface adapted to mount a lower dental casting thereon, an upper structure relatively movable with respect to said base member, a rearward pair of concave bearings positioned on one of said base member and said upper structure, a rearward pair of bearing pins adapted to engage respectively said rearward pair of the concave bearings, said bearing pins being positioned upon the other of said base member lit and said upper structure, a forward concave bearing secured to one of said base member and upper structure, a bearing pin for slidable enent therewith secured to the fore of other of s: base member and said upper structure, each of concave bearings having indentations at the most recessed position therein for indicating, in conjunction with said bearing pins, the centric position of the upper jaw casting with relation to the lowering jaw casting, and deviations of the bearing pins from their centric relation with the concave bearings simulating the relative movement of the jaws in a dentulous human mouth with the facets of the occlusal surface of the upper and lower teeth operating in natural contact.

6. The subject matter of claim 5, in which said conjoining bearing surfaces are adjustable in lengthwise relation between the base member and the upper structure, alignment with said indentations serving to establish a parallel relation between the base member and the upper structure as well as defining the centric relation between upper and lower jaw castings.

HAROLD J. THOMPSON.

Name Date Gysi June 5, 1917 Number 

